Chapter 22 FlexCAN
MPC5602P Microcontroller Reference Manual, Rev. 4
572
Freescale Semiconductor
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Time Segment 1: This segment includes the Propagation Segment and the Phase Segment 1 of the
CAN standard. It can be programmed by setting the PROPSEG and the PSEG1 fields of the CTRL
Register so that their sum (plus 2) is in the range of 4 to 16 time quanta.
•
Time Segment 2: This segment represents the Phase Segment 2 of the CAN standard. It can be
programmed by setting the PSEG2 field of the CTRL Register (plus 1) to be 2 to 8 time quanta
long.
Eqn. 22-2
Figure 22-16. Segments within the bit time
gives an overview of the CAN compliant segment settings and the related parameter values.
Table 22-24. Time segment syntax
Syntax
Description
SYNC_SEG
System expects transitions to occur on the bus during this period.
Transmit Point
A node in transmit mode transfers a new value to the CAN bus at this point.
Sample Point
A node samples the bus at this point. If the three samples per bit option is
selected, then this point marks the position of the third sample.
Table 22-25. CAN standard compliant bit time segment settings
Time Segment 1
Time Segment 2
Resynchronization
Jump Width
5 .. 10
2
1 .. 2
4 .. 11
3
1 .. 3
Bit
Rate
f
Tq
number
of
Time
Quanta
Þ
Þ
Þ
-----------------------------------------------------------------------------------------
=
Þ
SYNC_SEG
Time Segment 1
Time Segment 2
1
4 ... 16
2 ... 8
8 ... 25 Time Quanta
= 1 Bit Time
NRZ Signal
Sample Point
(single or triple sampling)
(PR PSEG1 + 2)
(PSEG2 + 1)
Transmit Point